Structure formation patterns in carbamide synthesis of nanocrystalline graphite-like boron nitride

We have used chemical analysis, x-ray diffractometry, transmission and scanning electron microscopy, and also measurement of the specific surface area to study the characteristic patterns of nitriding and structure formation in graphite-like BN powders synthesized by the carbamide method under various conditions. We have studied the effect on the synthesis process from the ratio of boric acid to carbamide in the starting mixture, preliminary grinding of the charge, the nitriding temperature and time. We show that the major factor determining the composition and structure of the product synthesized at 900-1200 °C is the ratio of the starting components. Carbon-free BN of stoichiometric composition is formed for a 1: 3 ratio of boric acid to carbamide as a result of two-hour nitriding at 1200 °C. The graphite-like BN obtained is characterized by a turbostratic nanocrystalline structure with a specific surface area of 100 m^sup 2^/g and high nanoporosity of the powder particles.[PUBLICATION ABSTRACT]